UFC Fight Night 19 PosterUltimate Fighter 5 lightweight winner Nate Diaz will look to rebound from back-to-back losses when he takes on Melvin Guillard in the main event of UFC Fight Night 19 on September 16 in Oklahoma City.

The UFC announced the 155-pound matchup on Tuesday, with another lightweight matchup between Roger Huerta and Gray Maynard set to co-headline the Spike-televised card.

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After falling short in a WEC lightweight championship bout against Hermes Franca, Diaz (10-4) won The Ultimate Fighter 5 with a finals win over Manny Gamburyan. Following four-straight wins over Junior Assuncao, Alvin Robinson, Kurt Pellegrino, and Josh Neer, Diaz suffered the first setback of his UFC career, a split decision loss to Clay Guida in January. In his most-recent fight at The Ultimate Fighter 9 Finale in June, Diaz suffered a unanimous decision loss to Joe Stevenson.

Following a 3-1 start to his UFC career, Guillard (22-7-2) headlined UFC Fight Night 9 against Joe Stevenson but was submitted in just 27-seconds, then tested positive for cocaine and served an eight month suspension. After suffering a loss to Rich Clementi in his first bout after the suspension in late-2007, Guillard briefly left the promotion, earning a decision win over Eric Regan before returning with a “Knockout of the Night” of Denis Siver at UFC 86 last July. “The Young Assassin” was scheduled to take on Spencer Fisher at UFC 90 in October, but a torn ACL forced him out of the bout. Guillard returned to the Octagon at the TUF 9 Finale, picking up a split decision over Gleison Tibau.

In addition to Diaz-Guillard and Huerta-Maynard, UFC Fight Night 19 is rumored to include Dan Miller vs. Aaron Simpson, Chris Wilson vs. Mike Pyle, Jeremy Stephens vs. Ronny Torres, Tim Credeur vs. Nate Quarry, and Kyle Bradley vs. Sam Stout.

For the latest UFC Fight Night 19 rumors check out the MMAFrenzy.com UFC rumors section.